The present invention relates generally to a method for generating holes in laminate materials and more particularly to a method for generating holes in fiber-reinforced metal laminates (FML).
Laminate materials are used throughout the aircraft/aerospace industry. Laminate materials provide high strength/low weight structural characteristics that are often crucial to aircraft applications and design. One group of laminate materials are known as fiber-reinforced metal laminates (FML). Fiber-reinforced metal laminates are hybrid composites consisting of alternating layers of metal sheets and fiber-reinforced epoxy pre-preg. The FML concept is known to combine the favorable properties of metals and composites while reducing their disadvantages. The aeronautics/aerospace industry has recognized significant weight and cost savings through the utilization of these materials and has discovered that these materials can be applied to many primary structures. Although a wide variety of individual metals and composites may be utilized to form FML materials, one known FML grouping is referred to as titanium graphite FML material.
Although fiber-metal laminates are recognized as providing a variety of costs and weight savings to aircraft structures, they are also known to create difficulties in the manufacturing and processing of structures utilizing them. One such manufacturing difficulty is known to arise during the drilling and/or boring of holes within the FML material. These manufacturing difficulties have been found to increase when performed on titanium/graphite fiber-metal laminate materials. These difficulties commonly take the form of burs and delamination experienced by the titanium/graphite fiber-metal laminate when exposed to the drilling or cutting process.
Resultant burring and delamination can present impediments to many aeronautics/aerospace applications. Localized weaknesses resulting from burring or delamination as a result of drilled holes are often located precisely where weakening can least be afforded. Furthermore, aircraft assemblies often rely on smooth surfaces for improved aerodynamics and increased efficiency. The presence of burring and delamination, therefore, can run counter to these fundamental desires. It would, therefore, be highly desirable to have a method for producing drilled or cut holes within fiber-metal laminate materials that reduced and/or eliminated the production of burs and delamination. It would further be highly beneficial to have a method for producing such burless and delamination free holes that would also improve cutter life and overall cost of manufacture.
It is, therefore, an object of the present invention to provide a method for creating holes in fiber-metal laminate material with reduced spur direction. It is a further object of the present invention to provide a method for creating holes in fiber-metal laminate materials with reduced incidents of delamination.
In accordance with the objects of the present invention, a method of generating holes in fiber-metal laminate material is provided. The method includes utilizing a cutter to create a first bore in the fiber-metal laminate material. The first bore is created by moving the cutter from a first side of the fiber-metal laminate material to a second side of the fiber-metal laminate material to create the first bore containing at least one tapered portion positioned adjacent the second side of the fiber-metal laminate material. The method further includes passing the cutter through the first bore and taking the cutter outwards of the at least one tapered portion. Finally, the method includes retracting the cutter to the first bore to create a second bore. The second bore has straight sides.